The present invention relates to a single-twist bunching or stranding machine of the type which includes feed spools for the stock to be stranded, stranding means such as a stationary stranding disc, and a stranding nipple, head, or die, a flyer carrying deflecting pulleys, and a receiving spool or reel being axially displaceable but otherwise mounted inside of the flyer: the flyer is driven by a motor which also drives the receiving spool.
Stranding machines or bunching machines of the type referred to above can be used to make stranded wires, serving as individual conductors. In addition, such a machine can be used for stranding together several conductors or even groups of conductors such as pairs or quads, the latter having been stranded upstream in analogous fashion so that, in effect, a serial or cascading operation of stranding is provided by a plurality of this type of machine. Stranding machines have also been used to provide shields onto insulated conductors or conductor cores. It should be understood, therefore, that stranding elements within the context of this invention, include individual metallic wires or filaments, twisted or stranded wires or conductors, or groups of stranded conductors, etc. In order to facilitate the description of the invention, the stranding of wire filaments to obtain a metallic, stranded wire is used to describe the invention, but it will be understood that the principles thereby explained are applicable to larger units as referred to above.
Stranding of wires or filaments to obtain metallic, multi-wire conductors is particularly employed when the number of wires or filaments to be stranded together is quite large. Generally speaking, one distinguishes between single-twist bunching or stranding and double-twist bunching or stranding. The single-twist stranding machine has the advantage that the resulting multi-wire conductors have very accurate and very accurately predetermined dimensions, and their overall configuration is a highly uniform one. The known single-twist stranding machines are disadvantaged by a rather low manufacturing speed. Still, one has used a single-twist bunching or stranding machine as mentioned above, particularly in those cases in which uniformity and accuracy are of overriding importance. Such highly accurately made conductors are, for example, used in the electrical systems of aircrafts where the diameter of the wires and the utilization of high-quality insulating materials require small dimensions, particularly because of the weight problem in aircraft manufacturing. It can readily be seen that, in this case, accuracy is of overriding importance. On the other hand, a double-twist stranding or bunching machine operates at about a three-fold speed, but the quality of the stranded product is low. One will use this double-twist machine in those cases in which the lower quality can be tolerated, but wherein speed of manufacturing is of overriding importance.
A particularly known single-twist stranding machine is, for instance, constructed to have a stationary distributor disc and a rotating nipple, head or die, in which about 19 wires coming from individual supply spools are combined and stranded together. A withdrawal sheave or capstan and deflection pulleys run the stranded system to a receiving spool for being wound thereon. In order to provide differently long lays in the multi-wire conductor, the machine includes exchangeable wheels, particularly to obtain a step-wise change in stranding length or length of lay. The conductor as made is run over deflection pulleys arranged on the flyer for purposes of winding the stranded conductor onto the receiving spool. The flyer rotates about the same axis as the receiving spool and, in effect, revolves about the latter. In order to permit winding the completed conductor in layers onto the receiving spool, the latter is positioned and moved over its entire length in axial direction. This known machine also includes a brake in order to stop the receiving spool in those cases in which the wire ruptures for any reason. The brake is usually constructed as an induction brake and its braking force is adjustable accordingly. Moreover, the brake is used to some extent during regular operation in that it applies some braking force to the receiving spool during winding of the stranded conductor so that the speed of rotation of the receiving spool is a little below the speed of rotation of the flyer. These two devices are driven by a common motor. By cooperation of these various devices and in correspondence with the withdrawal speed of the caps of the withdrawing capstan, the completed conductor is wound in layers onto the receiving spool.
The brake mentioned above and acting upon the receiving spool is adjustable corresponding to the manufacture of different conductors with a different number of wires or to accommodate wires having different diameters. However, during operation, a running control of the braking force is not provided for in these known devices, so that there is no compensation for the change in winding diameter of the receiving spool when it begins to fill up. Therefore, it is unavoidable that the conductor experiences during manufacture a variable tension, which, in turn, interferes with uniformity in the stranding assembly of the conductor. Another disadvantage of the known machine is to be seen that in the case a wire tears, the motor is stopped and the flyer is also stopped quickly by means of a mechanical brake, but the receiving spool continues to rotate because the induction brake acts somewhat slower. Consequently, the multi-wire conductor is strongly tensioned and may even tear in its entirely. It can readily be seen that it is quite complicated to return such a machine to normal operation once a wire does tear.